Japanese patent application No. 43-54280/1968, published Mar. 25, 1971, as Japanese Pat. No. 46-11679/1971 discloses a class of dithiobiurets of the general formula ##STR3## where R.sup.1 and R.sup.2 can be hydrogen or lower alkyl and R.sup.3 and R.sup.4 can be hydrogen, lower alkyl, cyanoalkyl, formyl, acetyl, halogen acetyl, and pyridyl. These compounds are said to be useful as insecticides, housefly antifertility agents, and mite-killing agents.
It has been found, however, that these compounds exhibit undesirable levels of phytotoxicity. It is this problem that the compounds of the present invention have overcome. Compounds of the present invention provide excellent protection against mites without causing any significant damage to the treated plants.